This invention relates to foot operated electrical controls and more particularly relates to a foot operated mechanism which may determine the angular position of the shaft of a potentiometer or other rotatable control device as well as the operation of switches.
Mechanisms for controlling the operation of foot operated switches and potentiometers which vary resistance by rotation of a shaft are well known. A commonly used mechanism is one in which a potentiometer has a pinion mounted to its shaft and the pinion is engaged by a gear segment or arm which upon pivotal movement rotates the shaft mounted pinion. Such an arrangement is exemplified in U.S. Pat. No. 5,535,642. This arrangement requires the provision of and mounting of a pinion to the potentiometer shaft and further the definition of a segment of a gear on the pivotal operating arm. While this mechanism has found widespread use, it has an operating drawback in that the meshing teeth of the gear and pinion may not provide smooth operation because of the increments of rotation defined by the teeth and also backlash in the teeth.
Another somewhat similar arrangement has been to place a wheel on the shaft of a potentiometer, which is engaged by an arcuate surface or end of a pivotal operating arm. This arrangement is rather expensive in requiring tight tolerances and additionally a force to hold the roller and arcuate surface or end of operating arm in contact. A further factor, which must be considered, is the play or sloppiness in the bearing for the potentiometer shaft. These considerations make the latter mentioned construction rather expensive.
Accordingly, the present invention provides a new and improved operating mechanism for a potentiometer mounted for foot operation which is smooth and accurate in operation and which is of reduced construction cost.
An object of this invention is to provide a new and improved foot operated mechanism for producing rotary motion of the shaft of an electrical element.
Another object of this invention is to provide a new and improved mechanism for controlling the angular position of a rotatable shaft, which is simple in construction and economical in cost.
A further object of this invention is to provide a new and improved foot operated mechanism of simplified design and economical cost for producing rotation of the shaft of an electrical element such as a potentiometer.
A still further object of this invention is to provide a new and improved pivotal connection between the base and treadle members of a foot operated electrical control.
Briefly stated, the invention, in one form thereof, comprises apparatus for foot operating an electrical element having a rotatable shaft comprising a base member adapted to be secured to a floor and defining a top opening cavity. A shaft is journaled in opposite side walls of the base member for rotation or pivotal motion therein and a treadle member is mounted to said shaft and arranged to rotate the shaft when depressed by foot pressure. A support member is secured to the base member within the cavity and has at least one upstanding wall. An electrical element such as a potentiometer having a rotatable operating shaft is mounted to the at least one upstanding wall. An operating arm is mounted at one end thereof to said shaft and has a bent over free end defining an elongated arcuate surface adjacent the operating shaft. A flexible cord is connected at one end thereof to the operating arm at a location toward the mounting of the operating arm to the shaft. The cord extends over a portion of the arcuate surface, is spirally wound a plurality of times about the operating shaft, continues over said surface and is anchored at its other end to said operating arm. The cord is of a fixed length. Upon depression of the treadle and rotation of the shaft, the cord moves along the elongated surface surface, while frictionally engaging the operating shaft, and rotates the shaft in accordance with the amount of depression of the treadle member.
The features of the invention which are believed to be novel are particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, together with further objects and advantages thereof may best be appreciated by reference to the following detailed description taken in conjunction with the drawings.